Without limiting the scope of the invention, its background is described in connection with current methods of etching metal oxides, as an example.
Metal oxide materials such as niobium pentoxide (Nb.sub.2 O.sub.5), because of their electrical and mechanical properties, having found many uses in the field of electronics. The very high dielectric constants exhibited by many metal oxide compounds make them useful as the dielectric material in capacitors, especially in the miniature capacitors which are built into many integrated circuits (e.g. dynamic RAMs). Many metal oxide materials also have a positive temperature coefficient of electrical resistance, which allows devices to be made which protect electrical motors from damage due to over-current conditions. The piezoelectrical properties of these materials are widely used, as in the precise control of the length of laser cavities, for example. Microminiature structures which incorporate metal oxide material are being used to sense infrared radiation, obviating the need for bandgap detector materials which require cryogenic cooling to sense the infrared.
Metal oxide materials are often etched during the fabrication of the electrical devices which exploit their beneficial properties. A method used to etch metal oxides should generally do so without introducing damage which would unacceptably change the properties of the material on which the function of the eventual devices depends. In addition, an anisotropic etch method is usually desired so that detail in the etch mask pattern is preserved. Contamination of the metal oxide material (and/or nearby materials) by the etch method usually cannot be tolerated.
Heretofore, in this field Nb.sub.2 O.sub.5 has been etched by isotropic wet etching using highly concentrated hydrofluoric acid (e.g. 49% HF).